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Finding the Fourth Proportional to 859.10, 1,287.30 and 640.40

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Solution

The fourth proportional to 859.10, 1,287.30 and 640.40 is: 959.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    859.10 : 1,287.30 = 640.40 : x
  2. Step 2: Convert to fraction form
    859.10/1,287.30 = 640.40/x
  3. Step 3: Cross multiply
    859.10x = 1,287.30 × 640.40
  4. Step 4: Simplify right side
    859.10x = 824,386.92
  5. Step 5: Solve for x
    x = 824,386.92/859.10
  6. Step 6: Final answer
    x = 959.59

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.